This invention relates to assist rod assemblies for throwing railway switch points.
Railway switches generally include a switch machine mounted on the outside of the rails adjacent the turnout points. The switch machine actuates a throw rod that is connected to a switch rod extending between the switch points.
A lost motion device, commonly referred to as a basket, may be provided between the throw rod and the switch rods to take up some of the motion of the throw rod before transmitting it to the switch rods. The basket enables a signal maintainer to adjust both the initial position and the throw of the switch rod to account for differing design applications of the rods and the total linkage length of the rod and to compensate for differing design locations of the switch machine in relation to the switch point.
In order to ensure coordinated movement between the point and heel ends of the movable rails, assist rods are used with longer switch points. For convenience the point and heel ends of the assembly are referred to as the front and rear ends respectively. The assist rods act to transfer force from the front end switch rods to those at the rear end. Operating or throw rods extend from the switch rods to the assist rod. The assist rod extends along the outside of the running rail, but on the side of the tracks opposite to the switch machine. This is done to accommodate the clearance requirements between switch accessories and the rail (to allow for tamping and protection from dragging equipment on passing trains). Juxtaposing the switch machine and the assist rod would require unusually long ties to maintain the necessary clearance.
In a typical arrangement, the throw rod is connected to the switch rods by means of a basket. The switch rods are in turn connected to the switch point (rails). The switch rods are also connected to a connector rod that extends under the running rail to a crank stand located on the outside of the running rail. The crank stand includes a lever, one end of which is connected to the connector rod and the other end of which is connected to an elongated assist rod running parallel to the running rail. The lever is mounted on a hinge on the crank stand such that when the connector rod causes one end of the lever to rotate about the hinge, the other end causes axial displacement of the assist rod. The assist rod is attached at its rear end to a similar lever and crank stand assembly that is in turn connected to a connector rod. The rear end connector rod is connected to a basket which transfers movement of the connector rod to the rear end switch rods.
It has also been proposed to used a torsional assist rod mounted on the side of the track that is distal from the switch machine. The assist rod is connected by a pin to the end of the switch rod or to the end of a connector rod. Displacement of the front end switch rod causes the assist rod to rotate. By a similar arrangement at the rear end, rotation of the assist rod throws a connector rod connected to the rear end switch rod. It is also known to locate torsional assist rods between the rails.
One disadvantage of prior art assist rod assemblies is that the basket is located between the rails to allow for tamping on the outside of the rails. However, the location of the baskets between the rails results in limited accessibility due to hot air ducts used for snow removal that are frequently mounted between the rails over the top of the basket. In addition, the signal maintainer must place himself in the direct path of oncoming rail traffic to service or adjust the device.
In addition, the switch ties must accommodate both a switch machine (on one end) and an assist rod and its associated linkage components (on the other end). As a result, relatively long ties (typically 14 feet long) are needed. In the case of crowded rail yards, the loss of space resulting from adjacent switches becomes critical.
It is an object of the present invention to provide an improved assist rod assembly that overcomes the foregoing deficiencies.
The invention provides an assist rod assembly wherein the point end and heel end baskets are located between the running rail and the switch machine. The throw rod and the baskets are seated in a hollow tie that also houses the switch rod.
The baskets of the invention play a dual role. They both take up lost motion and they actuate the assist rod.
The front basket includes an upwardly extending head portion adapted to link to a torsional assist rod and to rotate the assist rod when the basket undergoes lateral movement (transverse to the running rails) as a result of the switch being thrown.
The head of the basket comprises a bore for receiving a pin for rotation in the bore. A pair of link arms extend from the ends of the pin. The link arms engage the assist rod to cause it to rotate when the basket undergoes lateral movement transverse to the assist rod. The assist rod is separately mounted for rotation in a sleeve on a support clip. The basket comprises an internal structure similar to prior art structures. A threaded connector rod slidably extends through the basket. Movement of the basket in relation to the connector rod is limited by nuts threaded onto the rod at each end of the basket. Adjustement of the nuts serves to adjust the amount of lost motion to be taken up by the basket before actuating the connector rod by abutment of the basket with the nuts.
The rear basket comprises two link arms, one end of which arms engage the assist rod. The other ends include opposed pins rotatable within bores in the link arms. The pins are connected to a slide block through which a threaded connector rod is slidably received. Nuts are disposed on the connector rod at each side of the slide block so as to enable adjustment of the amount of free motion that the basket will be allowed to undergo before actuating displacement of the connector rod by abutment of the basket to the nuts.
The provision of the baskets in hollow ties avoids the need to worry about the baskets interfering with tamping.
The invention allows for a more compact switch assembly in which the baskets and the assist rod may be located on the same side of the rails as the switch machine. This in turn allows for the use of shorter ties.
The invention also has the advantage of comprising a smaller number of components than the assist rod assemblies of the prior art.